MitchStellin

I use 20-50. I would like to go to Mobile 1 but I hear so many worries about going to synthetic oil. I also hear on a full roller motor to stay away from the synthetic because it does not work with the extra tolerance our motors have, it is also so slippery that the rollers may not roll and develop flat spots. I have 502s with the HP kit, full roller (crane gold) and Dart intake. What do you guys think? I was told this by a very reliable engine builder.

robyw1

That is a myth. I heard the same things too Mitch and it is an old engine builders wives tail. If the roller didn't roll because it was so slick that would be fine with me. It would be riding on a thin sheen of oil and cause no wear. If your roller lifters are hanging up then you should have a talk with the manufacture. The only time I ever lost a roller cam was when it broke. Thank you Iskenderian

The only time you shouldn't use it is during engine break-in when piston rings need more friction than normal to properly seat. Also in leaky engines synthetic oil can exploit those leaks and be worse.

Roby

Monty

The main difference synthetic motor oil has versus a conventional motor oil is at the molecular level. Synthetics do not have the waxes, ash, etc and other impurities that conventional motor oils have, and their molecular structure is uniform compared to conventionals. These impurities that conventionals have burn off a different temps or contribute to deposit formation.

Mobil 1, for example, is the factory fill motor oil for many higher-end production cars, most of which have roller or OHC valvetrains. Do you think GM would put Mobil 1 in Corvettes if it were going to cause unusual valvetrain wear that they would have to address under warranty? Actually, even in automotive apps with conventional motor oils, roller tipped rocker arms have a tendency to slide over the valve stem rather than roll, especially under higher vlave spring pressures. But you're only talking about a movement of 1/3 of 11/32 of an inch(typical in a GM engine). The late John Lingenfelter even pointed this out in his engine book, and I have seen this myself while setting up valve trains. Of course my observations occured while rotating the engine by hand, which is entirely different than an engine operating at thousands of rpm.

I see or hear people say all the time how marine engines have extra clearances in comparison to automotive engines, but that's not really true. It's a good idea to consider the fact that most marine engines perform at a lower operating temperature which may affect piston to cylinder wall clearance due to the fact that the cylinder block doesn't get as hot and wrist pin clearances due to potentially higher piston temps as a result of running under load for extended periods, but other critical clearances such as main and rod bearings, valve guides, etc are the same as automotive applications. If you open the clearances up too far out of tolerance, then you lose oil pressure and oil film strength. Metal to metal contact results.

The cylinder walls and pistons/rings and wrist pins are primarily lubricated and cooled by oil splash. As long as the cylinder walls are machined appropriatelyfor the piston ring, i.e. moly, excessive oil consumption is not a problem. It used to be said that you shouldn't break an engine in on synthetics because the rings wouldn't seat as well, but with modern honing techniques even that is not a problem. The only drawback synthetics have compared to conventionals is their increased cost.

Chase910

My engine builder ( Innovation Marine ) says to use in my 502/500hp Mobil 1 15/50w. When talking to them about this they said after testing on the dyno..Mobil 1 worked best and gave 10hp over straight weight.

Chris288

I know this had been debated to death, but there is always some GOOD information that comes out of these threads... I was thinking of going with castrol 20-50 synthetic BLEND, I now have 12 hours on a new 496 H.O. The blend seems like the best of both worlds..

mr_velocity

Got basically the same motor, 509 cu in, full roller crane gold, even have the dart intake. For the 2 years I ran Red Line 50W Race, the past 2 years Mobil 15W50. No problems after many hard hours.

MitchStellin

Thanks for the info, I am going to Mobile 1, my engine has about 40 hours or so on since rebuild so the break in is done. I have a cool oil change system on this boat, lines from the drain plugs go to a T and then to a pump on the bulkhead. The T has valves so you can isolate each engine, put a 5 gal bucket on the ground (long line from pump to bucket, but a siphon effect helps pump fast) and you are done, I have a 5 gal with a lid and a small hole for the hose. I can dump a pan in about 2 min. I can even reverse it to pump in but that makes no sense. I am off tonight to buy 20 qrts Although more costly, the extended life of the oil will offset this cost....by a bit, I change every 50. Thanks for the tech info, like said, why would Corvette use this from day one if it was not the best.

stecz20

royal purple.........

ActiveFun

I have a 540 w/871 blower at 5lbs of boost. No intercooler. I've been told to use Kendall Racing 20/50. What do you think?? (I change the oil every 10 hours)

ActiveFun

My engine builder recommended it in the beginning. Since I change it about every 10 hours, Im told it's ok. They don't recommend synthetic.